Catalysts containing titanium compound supported on active magnesium halide, and electron donor compound are well known in the art.
U.S. Pat. No. 4,544,717 discloses that the stereospecificity of catalysts can be improved by adding electron donor compounds (i.e. internal electron donor) to solid component containing titanium compound. GB 2,111,066 discloses that contacting magnesium chloride alcohol adduct with liquid titanium compound, adding a kind of electron donor (such as phthalates) simultaneously to form solid titanium catalysts, and adding another kind of electron donor (alkoxy silicon compound) during the polymerization of olefins, both of the activity and specificity of such catalysts can be substantially improved, and the processes of deliming and removing random materials can be eliminated. So far, various kinds of internal electron donor compounds suitable for preparing Z—N catalysts and catalysts for olefin polymerization containing such internal electron donor compounds have been disclosed in many patents.
Such internal electron donor compounds mainly include: 1,3-diketones compounds described in Japanese patent JP61231008, isocyanates compounds described in U.S. Pat. No. 6,143,684, succinates compounds described in European patents EP1165113 and EP1088009, 1,3-diethers compounds described in European patents EP0361494 and EP0728769, alkoxyketones compounds described in Chinese patent CN1850868, alkoxyesters compounds in Chinese patent CN1446787, malonate esters compounds described in U.S. Pat. No. 6,281,301, U.S. Pat. No. 6,294,497, U.S. Pat. No. 6,048,818 and PCT international application WO0026259 and diamines compounds described in Chinese patent CN1087918.
Using different internal electron donor compounds make the catalysts thus prepared have different properties. For example, some catalysts have higher activity, some catalysts have better hydrogen sensitivity, and polyolefin resin made from some catalysts has wider molecular weight distribution, and the like. However, in the industrial production of polyolefin, it is very desirable that the catalysts used have good comprehensive properties. In the prior art, various kinds of internal electron donor compounds are added during the preparation of catalysts so as to improve the comprehensive properties of catalysts. The preparation of catalysts component and catalysts for olefin polymerization by using two or more kinds of internal electron donor compounds simultaneously has been described in the publication patents JP2001139621, JP2002249507, WO9957160, KR20000026517, WO0230998, WO03002617, etc., but the results are not satisfactory. Generally, although the molecular weight distribution of the resulted polymer can be widen due to utilization of two or more kinds of internal electron donor compounds, the activity of catalyst then decreases.